A starter-generator device comprises a starter-generator, which is a reversible electrical machine.
A starter-generator is intended to be coupled mechanically to a shaft of a motor. It is able to operate in generator mode, during what is termed a generation phase, during which the motor provides motive power to the starter-generator. During this phase, the starter-generator transforms the mechanical rotational energy of the shaft of the motor into a polyphase AC electrical current intended to supply a user electrical network. The starter-generator is also able to operate in starter mode, during a startup phase, during which it transforms electrical energy that is provided thereto into a motive power intended to drive the shaft of the motor in rotation so as to start up the motor.
This type of starter-generator conventionally comprises a stator, comprising a polyphase stator winding, and a rotor, comprising a single-phase or polyphase rotor winding, that are coupled magnetically to one another. The stator winding and the rotor winding are coupled magnetically to one another. The rotor and the stator are for example the rotor and the stator of a main electrical machine in the case of a brushless starter-generator. The starter-generator is intended to be coupled mechanically to the shaft of the motor via its rotor.
In order to ensure startup of the motor, the stator winding is conventionally supplied by way of an AC current, thereby producing a rotating magnetic field in the stator. The rotor winding of the main machine is also supplied with DC current, thereby generating a magnetic field in the rotor of the starter-generator. The rotor and the shaft are then driven in rotation, and drive the shaft of the motor in rotation, thereby making it possible to start up the motor. The starter-generator then changes to generator mode when the motor has reached its idle speed. The supply for the stator and rotor windings is conventionally achieved by way of a starter regulation device, which is itself conventionally supplied by way of a power source via a DC supply bus. The motor is intended to rotate in a predetermined direction of rotation during the startup and generation phases. This direction of rotation is called the nominal direction of rotation.
APUs and aeronautical propulsion engines may comprise fins engaging with the surrounding air. The wind may then drive these engines in rotation, in the direction opposite to the nominal direction of rotation.